U.S. patent application number 12/487511 was filed with the patent office on 2010-12-23 for direction finding and geolocation of wireless devices.
This patent application is currently assigned to BAE SYSTEMS Information and Electronic Systems Integration Inc.. Invention is credited to Peter Dusaitis, John J. Kelly, Tyler Robinson, Joseph Warner.
Application Number | 20100321242 12/487511 |
Document ID | / |
Family ID | 43353844 |
Filed Date | 2010-12-23 |
United States Patent
Application |
20100321242 |
Kind Code |
A1 |
Robinson; Tyler ; et
al. |
December 23, 2010 |
DIRECTION FINDING AND GEOLOCATION OF WIRELESS DEVICES
Abstract
Techniques are disclosed that allow for the detection,
identification, direction finding, and geolocation of wireless
emitters in a given multipath environment. For example, the
techniques can be used to detect and identify a line of bearing
(LOB) to an IEEE 802.11 emitter in a building or in an open field
or along a roadside. Multiple LOBs computed from different
geographic locations can be used to geolocate the target emitter.
The techniques can be embodied, for instance, in a vehicle-based
device that can survey the target environment, detect an IEEE
802.11 emitter and identify it by MAC address, and then determine
various LOBs to that emitter to geolocate the emitter. In some
cases, a sample array of response data from the target emitter is
correlated to a plurality of calibrated arrays having known
azimuths to determine the LOB to the target emitter.
Inventors: |
Robinson; Tyler; (Merrimack,
NH) ; Dusaitis; Peter; (Manchester, NH) ;
Kelly; John J.; (Groton, MA) ; Warner; Joseph;
(Burlington, MA) |
Correspondence
Address: |
BAE SYSTEMS
PO BOX 868
NASHUA
NH
03061-0868
US
|
Assignee: |
BAE SYSTEMS Information and
Electronic Systems Integration Inc.
Nashua
NH
|
Family ID: |
43353844 |
Appl. No.: |
12/487511 |
Filed: |
June 18, 2009 |
Current U.S.
Class: |
342/445 |
Current CPC
Class: |
G01S 3/48 20130101; G01S
5/0252 20130101 |
Class at
Publication: |
342/445 |
International
Class: |
G01S 5/04 20060101
G01S005/04 |
Claims
1. A method for geolocating a wireless emitter, the method
comprising: measuring one or more response signal parameters for
each of Y antenna patterns, thereby providing a Y sample array of
response data from a target wireless emitter, wherein Y is greater
than 1; correlating the sample array to a plurality of entries in a
database of calibrated arrays having known azimuths, to determine a
line of bearing (LOB) to the target wireless emitter; repeating the
transmitting, measuring and correlating to determine one or more
additional LOBs to the target wireless emitter, each LOB computed
from a different geographic location; and geolocating the target
wireless emitter based on the LOBs.
2. The method of claim 1 further comprising the preliminary steps
of: surveying an area of interest to identify wireless emitters
within that area; and selecting a target emitter discovered during
the survey.
3. The method of claim 2 wherein the target emitter is associated
with a media access control (MAC) address and communication channel
that is learned during the survey, and the method further includes
transmitting a stimulus signal to the target emitter using the MAC
address and communication channel.
4. The method of claim 1 wherein the correlating step comprises:
generating a correlation plot having a peak using correlation
factors resulting from correlation of the sample array to the
plurality of entries in the database; identifying a target azimuth
of the sample array based on the peak of the correlation plot; and
determining the LOB to the target wireless emitter based on the
target azimuth.
5. The method of claim 1 wherein each of the LOBs is associated
with position and heading tags provided by a global positioning
satellite (GPS) module to assist in geolocating the target wireless
emitter.
6. The method of claim 1 further comprising: graphically displaying
the LOBs to the target wireless emitter.
7. The method of claim 1 further comprising: storing the
geolocation of the target wireless emitter.
8. The method of claim 1 wherein there are 64 or 4096 antenna
patterns.
9. The method of claim 1 wherein the one or more response signal
parameters include response signal amplitude.
10. The method of claim 1 wherein the method is carried out using a
vehicle-based device.
11. A system for geolocating a wireless emitter, the system
comprising: an antenna array for measuring one or more response
signal parameters for each of Y antenna patterns, thereby providing
a Y sample array of response data from a target wireless emitter,
wherein Y is greater than 1; a line of bearing module for
correlating the sample array to a plurality of entries in a
database of calibrated arrays having known azimuths, to determine a
line of bearing (LOB) to the target wireless emitter; and a
geolocation module for geolocating the target wireless emitter
based on multiple LOBs to the target wireless emitter, each LOB
computed from a different geographic location.
12. The system of claim 11 wherein the system is further configured
for surveying an area of interest to identify wireless emitters
within that area, the system further comprising: a user interface
for allowing a user to select a target emitter discovered during
the survey.
13. The system of claim 12 wherein the target emitter is associated
with a media access control (MAC) address and communication channel
that is learned during the survey, and the system further comprises
a transceiver configured for transmitting a stimulus signal to the
target emitter using the MAC address and communication channel.
14. The system of claim 11 wherein the line of bearing module is
configured for generating a correlation plot having a peak using
correlation factors resulting from correlation of the sample array
to the plurality of entries in the database, and identifying a
target azimuth of the sample array based on the peak of the
correlation plot, and determining the LOB to the target wireless
emitter based on the target azimuth.
15. The system of claim 11 wherein each of the LOBs is associated
with position and heading tags provided by a global positioning
satellite (GPS) module to assist in geolocating the target wireless
emitter.
16. The system of claim 11 further comprising: a user interface for
graphically displaying the LOBs to the target wireless emitter.
17. The system of claim 11 further comprising: a database for
storing the geolocation of the target wireless emitter.
18. The system of claim 11 wherein the system is configured for
vehicle-based operation.
19. A vehicle-based system for geolocating a wireless emitter, the
system comprising: a user interface for allowing a user to select a
target emitter discovered during a survey conducted by the system,
wherein the target emitter is associated with a media access
control (MAC) address and communication channel that is learned
during the survey; a transceiver for transmitting a stimulus signal
to a target wireless emitter using the MAC address and
communication channel; and an antenna array for measuring one or
more response signal parameters for each of Y antenna patterns,
thereby providing a Y sample array of response data from the target
wireless emitter, wherein Y is greater than 1, and the one or more
response signal parameters include response signal amplitude; a
line of bearing module for correlating the sample array to a
plurality of entries in a database of calibrated arrays having
known azimuths, to determine a line of bearing (LOB) to the target
wireless emitter; a geolocation module for geolocating the target
wireless emitter based on multiple LOBs to the target wireless
emitter, each LOB computed from a different geographic location;
and a user interface for graphically displaying the LOBs to the
target wireless emitter.
20. The system of claim 19 wherein the line of bearing module is
configured for generating a correlation plot having a peak using
correlation factors resulting from correlation of the sample array
to the plurality of entries in the database, and identifying a
target azimuth of the sample array based on the peak of the
correlation plot, and determining the LOB to the target wireless
emitter based on the target azimuth.
Description
RELATED APPLICATIONS
[0001] This application is related to U.S. application Ser. No.
______ (Attorney Docket BAEP-1122), filed Jun. 18, 2009, and titled
"Direction Finding of Wireless Devices." This application is also
related to U.S. application Ser. No. ______ (Attorney Docket
BAEP-1125), filed Jun. 18, 2009, and titled "Tracking of Emergency
Personnel." Each of these applications is herein incorporated by
reference in its entirety.
FIELD OF THE INVENTION
[0002] The invention relates to wireless communications, and more
particularly, to techniques for direction finding and/or
geolocating wireless devices such as those configured with IEEE
802.11 emitters and other such detectable emitters.
BACKGROUND OF THE INVENTION
[0003] Conventional techniques for locating IEEE 802.11 emitters
(e.g., access points as well as laptops with IEEE 802.11 capability
and other such clients) are based on measuring the amplitude of the
802.11 emitter with a portable receiver, and moving around to find
the direction in which the amplitude increases. The general
assumption is that the stronger the signal amplitude, the closer
the 802.11 emitter is believed to be. Several commercial devices
were developed for this purpose (e.g., Yellowjacket.RTM. 802.11b
Wi-Fi Analysis System).
[0004] There are a number of problems associated with such
amplitude-based techniques for locating 802.11 emitters. For
instance, the techniques tend to be highly inaccurate due to the
incidence of RF multipath created by the RF waveforms emanating
from the 802.11 emitters. These waveforms bounce off conductive
objects or surfaces in the environment, which causes multiple false
readings on increased amplitude (false directions) that then
disappear as the user leaves the multipath. Thus, conventional
amplitude-based locationing techniques will create many false high
amplitude paths to the target that will be incorrect, and will not
work in a high multipath environment, such as a neighborhood (e.g.,
street scene) or building (e.g., home, office building, or
cafe).
[0005] There is a need, therefore, for techniques that allow for
the detection, identification, direction finding, and geolocation
of wireless emitters in a given environment.
SUMMARY OF THE INVENTION
[0006] One embodiment of the present invention provides a method
for geolocating a wireless emitter. The method includes measuring
one or more response signal parameters for each of Y antenna
patterns, thereby providing a Y sample array of response data from
a target wireless emitter, wherein Y is greater than 1 (e.g., Y=64
or 4096; any number of antenna patterns can be used). The method
further includes correlating the sample array to a plurality of
entries in a database of calibrated arrays having known azimuths,
to determine a line of bearing (LOB) to the target wireless
emitter. The method further includes repeating the transmitting,
measuring and correlating to determine one or more additional LOBs
to the target wireless emitter, each LOB computed from a different
geographic location, and geolocating the target wireless emitter
based on the LOBs. The method may further include the preliminary
steps of surveying an area of interest to identify wireless
emitters within that area (e.g., using established discovery
protocols), and selecting a target emitter discovered during the
survey. This selection may be, for example, based on user input, or
done automatically based on some established selection scheme. In
one particular case, the target emitter is associated with a media
access control (MAC) address and communication channel that is
learned during the survey. In one such case, the method further
includes transmitting a stimulus signal to the target emitter using
the MAC address and communication channel. In another particular
case, the correlating step includes generating a correlation plot
having a peak using correlation factors resulting from correlation
of the sample array to the plurality of entries in the database,
identifying a target azimuth of the sample array based on the peak
of the correlation plot, and determining the LOB to the target
wireless emitter based on the target azimuth. In some cases, each
of the LOBs is associated with position and heading tags provided
by a global positioning satellite (GPS) module to assist in
geolocating the target wireless emitter. The method may include
graphically displaying the LOBs to the target wireless emitter,
and/or storing the geolocation of the target wireless emitter. The
one or more response signal parameters may include, for example,
response signal amplitude. The method can be carried out, for
example, using a vehicle-based device (e.g., truck, plane, ship,
etc).
[0007] Another embodiment of the present invention provides a
system for geolocating a wireless emitter. The system includes an
antenna array for measuring one or more response signal parameters
for each of Y antenna patterns, thereby providing a Y sample array
of response data from a target wireless emitter, wherein Y is
greater than 1. The system further includes a line of bearing
module for correlating the sample array to a plurality of entries
in a database of calibrated arrays having known azimuths, to
determine a line of bearing (LOB) to the target wireless emitter.
The system further includes a geolocation module for geolocating
the target wireless emitter based on multiple LOBs to the target
wireless emitter, each LOB computed from a different geographic
location. The system may be further configured for surveying an
area of interest to identify wireless emitters within that area. In
one such case, the system includes a user interface for allowing a
user to select a target emitter discovered during the survey. In
another such case, the target emitter is associated with a media
access control (MAC) address and communication channel that is
learned during the survey. In one such case, the system includes a
transceiver configured for transmitting a stimulus signal to the
target emitter using the MAC address and communication channel. In
another example case, the line of bearing module is configured for
generating a correlation plot having a peak using correlation
factors resulting from correlation of the sample array to the
plurality of entries in the database, and identifying a target
azimuth of the sample array based on the peak of the correlation
plot, and determining the LOB to the target wireless emitter based
on the target azimuth. In another example case, each of the LOBs is
associated with position and heading tags provided by a global
positioning satellite (GPS) module to assist in geolocating the
target wireless emitter. The system may include a user interface
for graphically displaying the LOBs to the target wireless emitter,
and/or a database for storing the geolocation of the target
wireless emitter. The system can be configured for vehicle-based
operation. A number of variations on this system will be apparent
in light of this disclosure.
[0008] The features and advantages described herein are not
all-inclusive and, in particular, many additional features and
advantages will be apparent to one of ordinary skill in the art in
view of the drawings, specification, and claims. Moreover, it
should be noted that the language used in the specification has
been principally selected for readability and instructional
purposes, and not to limit the scope of the inventive subject
matter.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIG. 1 illustrates a wireless emitter locating system
configured in accordance with an embodiment of the present
invention.
[0010] FIG. 2a illustrates a detailed block diagram of the wireless
emitter locating system shown in FIG. 1, configured in accordance
with an embodiment of the present invention.
[0011] FIG. 2b illustrates further details of the wireless emitter
locating system shown in FIG. 2a, configured in accordance with an
embodiment of the present invention.
[0012] FIG. 2c illustrates example states and modes of the wireless
emitter locating system shown in FIG. 2a, in accordance with an
embodiment of the present invention.
[0013] FIGS. 3a and 3b illustrate a vehicle-based version of the
wireless emitter locating system shown in FIG. 2a, configured in
accordance with an embodiment of the present invention.
[0014] FIG. 4 illustrates an example user interface of the wireless
emitter locating system shown in FIG. 2a, in accordance with an
embodiment of the present invention.
[0015] FIG. 5a illustrates a method for determining a line of
bearing to a wireless emitter, and geolocating that emitter, in
accordance with an embodiment of the present invention.
[0016] FIG. 5b illustrates a correlation process carried out by the
method of FIG. 5a, to identify which calibrated array best matches
a sample array, in accordance with an embodiment of the present
invention.
[0017] FIG. 5c illustrates a correlation scan or plot of
correlation coefficients resulting from the correlation process
shown in FIG. 5b, and having a peak that corresponds to an azimuth
(or LOB) to the target, in accordance with an embodiment of the
present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0018] Techniques are disclosed that allow for the detection,
identification, direction finding, and geolocation of wireless
emitters in a given multipath environment. For example, the
techniques can be used to detect and identify multiple lines of
bearing (LOBs) to IEEE 802.11 emitters in a building or in an open
field or along a roadside. The multiple LOBs can be used to
geolocate the target emitter. The techniques can be embodied, for
instance, in a vehicle-based device that provides a rapid and
accurate way to survey the target environment, detect active IEEE
802.11 emitters and identify them by MAC address, and then
precisely determine LOBs to each of those emitters to locate them
in or out of a building (or other multipath environment).
[0019] General Overview
[0020] Wireless communication devices, which are typically
configured with a networking card or a built-in chip or chip set,
are vulnerable to stimulation or otherwise exploitable for
on-demand direction finding. Typical such wireless devices include,
for example, laptop computers, cell phones and personal digital
assistants (PDAs), access points and repeaters, and other portable
communication devices. In addition, such devices typically include
a physical address (e.g., MAC address) by which they can be
identified and subsequently directly communicated with.
[0021] In accordance with one embodiment of the present invention,
a system is provided for direction finding wireless devices (e.g.,
IEEE 802.11 a/b/g/n/etc capable devices, all channels). The system
generally includes a wireless transceiver, a switchable antenna
array, and a direction finding algorithm that correlates measured
responses with calibrated responses to identify multiple LOBs to a
target wireless device. The system further includes a geolocation
algorithm. The wireless devices in the system's field of view (FOV)
can be targeted based on their specific MAC address (or other
suitable physical address or identifier).
[0022] In operation, the system initially carries out a survey
process, where the system discovers or otherwise detects wireless
emitters in its FOV. For instance, IEEE 802.11 discovery protocols
can be used by the system to discover and handshake with each
emitter in its FOV. During this discovery process, the system
learns information associated with the various emitters, such as
the responding emitter's media access control (MAC) address,
service set identifier (SSID), and/or communication channel. In
other embodiments, a network detector can be used to unobtrusively
detect and interpret information being transmitted by wireless
emitters in the FOV. Once this survey process is completed, the
system can then selectively target each of the discovered emitters
for direction finding and precise geolocation.
[0023] For instance, the system transmits a stimulus signal (e.g.,
an IEEE 802.11 compliant RF signal, or any suitable signal that
will cause a desired response signal) to stimulate a target emitter
based on that emitter's MAC address, and captures the response from
the target emitter. The switchable antenna array of the system
operates in synchronization with a transceiver, and allows for
response signal detection over numerous antenna array
configurations.
[0024] For example, an antenna array having six
horizontally-polarized switchable elements has up to 64 different
configurations (i.e., 2.sup.6). Other antenna array configurations
will be apparent in light of this disclosure. In any such cases,
one or more response signal parameters (e.g., amplitude, or
amplitude and phase) can be detected for each of the Y antenna
array configurations, so as to provide an array (having Y entries)
of response signal data associated with the target emitter. The
system's direction finding algorithm effectively converts this
array of measurements into an LOB relative to the current position
and orientation of array.
[0025] The geolocation algorithm can be used to accumulate two or
more LOBs from different vantage points to geolocate the precise
location of the emitter along an LOB (based on an intersection of
the LOBs and/or global positioning satellite (GPS) position and
heading tags associated with each computed LOB). The LOB and/or
geolocation can be communicated to the user, for example, via a
display or other suitable user interface. In one particular such
embodiment, results can be visually depicted on a map display or
polar plot to indicate in real-time the direction to and/or
location of the target device. The user interface may be further
configured to allow for control and tasking of the system, as will
be apparent in light of this disclosure.
[0026] The system and techniques do not interfere with service to
the target device (operation is effectively transparent to target
device). In addition, the techniques work at the hardware layer
regardless of device mode, thereby bypassing various impediments
such as encryption techniques, MAC address filters, and hidden
SSIDs. The system and techniques can be used for a number of
applications, such as finding 802.11 emitters in rural and urban
environments, or within a military zone. In addition, the system
and techniques can be used for mapping publicly accessible access
points (e.g., to identify unencrypted access points available for
free use). For instance, a website dedicated to providing an
on-line accessible database of known publicly accessible access
points may provide a business model for generating revenue. In one
such embodiment, revenue may be provided via fees received for
online advertising posted on the website, such as advertisements
related to the services and/or goods associated with the
brick-and-mortar business that is providing the public access
point. Other monetization schemes for such a database will be
apparent in light of this disclosure.
[0027] A number of system capabilities and features will be
apparent in light of this disclosure. For instance, the system can
be implemented in a compact fashion thereby allowing for form
factors amenable to vehicle-based or unmanned aerial vehicle (UAV)
configurations, and can be employed to survey, detect, identify,
direction find, and geolocate wireless emitters (e.g., 802.11
access points and clients, cell phones, PDAs, etc). The LOB to
and/or geolocation of such target emitters can be identified from
within the same building or from outside a building or in an
outdoor area or other multipath environments, thereby providing the
capability for precise locationing.
[0028] Other emitters vulnerable to stimulation (e.g., Bluetooth
emitters) and characterization can be detected using the techniques
described herein, and the present invention is not intended to be
limited to IEEE 802.11 emitters. In addition, note that the number
of antenna configurations provided will depend on the number of
switchable elements included in the array and whether or not those
elements are vertically-polarized and/or horizontally-polarized.
For instance, an antenna array having six switchable elements that
are each both vertically-polarized and horizontally-polarized has
up to 4096 different configurations (i.e., 2.sup.12).
[0029] Wireless Emitter Locating System
[0030] FIG. 1 illustrates a wireless emitter locating system 10
configured in accordance with an embodiment of the present
invention. The system 10 can be implemented, for example, in a
vehicle-based platform to allow for portable direction finding
and/or geolocationing in multipath environments.
[0031] As can be seen, system 10 is capable of transmitting
stimulus signals to its field of view (FOV), and receiving
responses from any number of wireless emitter devices 50 located in
that FOV. The example wireless emitter devices 50 depicted include
laptop 50a, PDA 50b, cell phone 50c, and wireless access point 50d.
Each of these devices 50 can be, for example, IEEE 802.11 compliant
wireless emitters. In a more general sense, devices 50 can operate
in accordance with any wireless communication protocol that allows,
for instance, discovery based on an established handshake or other
messaging technique by which devices 50 and system 10 make their
existence known to each other to establish communication links
there between. Other detection techniques, whether based on such
two-way messaging schemes or one-way covert detection mechanisms,
will be apparent in light of this disclosure.
[0032] Thus, system 10 may initially transmit a stimulus signal to
survey the currently available devices 50. The survey signal
transmitted by system 10 may be responsive to signals being
transmitted by the devices 50, or may be the initiating signal that
wakes-up devices 50 so that they can respond in accordance with an
established wireless communications protocol. During such discovery
processes, the devices 50 may share information about themselves
with system 10. For instance, devices 50 that are compliant with
IEEE 802.11 may share information including their MAC address,
SSID, channel, and current encryption status (e.g., encrypted or
not encrypted). In other embodiments, the discovery process can be
covert or otherwise transparent to the wireless emitters 50 in the
FOV. For instance, a network detector (such as KISMET or
NETSTUMBLER) can be used to detect and interpret information being
transmitted by wireless emitters in the FOV, thereby allowing
information such as MAC address, SSID, channel, and current
encryption status to be identified. Thus, pertinent information
about the potential target wireless emitters 50 in the system's FOV
can be acquired by a survey that uses at least one of discovery
protocols and/or network detection techniques, and the system 10
can then communicate with specific ones of the various available
target wireless devices 50, so as to direction find and/or
geolocate that target device.
[0033] The devices 50 can be located, for example, in a building or
outdoors in a park area or along a roadside. The system 10 can be
located in the same building, a different building, or outside as
well. In short, system 10 can direction find and geolocate devices
50 regardless of the environment (multipath or not) associated with
the respective locations of system 10 and devices 50. The distance
between the system 10 and devices 50 can vary depending on factors
such as transmit power and the communication protocols employed. In
an embodiment using IEEE 802.11 communication protocols, the
distance can be, for instance, out to hundreds of meters.
[0034] FIG. 2a illustrates a detailed block diagram of the wireless
emitter locating system 10, configured in accordance with an
embodiment of the present invention. As previously explained with
reference to FIG. 1, the system 10 is capable of identifying
potential target emitter devices, and computing one or more LOBs to
a target device. The system can then geolocate the target device on
the LOB, based on an intersection of LOBs from multiple vantage
points and/or GPS position and heading tags associated with each
computed LOB, as will be discussed in turn.
[0035] As can be seen, the system 10 generally includes a computer
200, a multi-element beamforming array 216, a GPS module 213 and
GPS antennas 213a-b, a network detector 215 and omni-directional
survey antenna 215b, an Ethernet hub 219, and an optional mapping
module 221. The multi-element beamforming array 216 includes an RF
transceiver 217 and a beamformer 218 that includes an RF switching
network 218a and a multi-element antenna array 218b. The computer
200 includes a user interface 201 having controls 201a and display
area 201b, a processor 203, and a memory 205. The memory 205
includes calibration files 209, a LOB module 207, and a geolocation
(Geo) module 211. Other conventional componentry not shown will be
apparent in light of this disclosure (e.g., busses, storage
mechanisms, co-processor, graphics card, operating system, user
interface mechanisms, etc). The system may be powered by batteries,
or may derive its power from other sources, such as a vehicle in
which the system is operating. A number of suitable power schemes
can be used here.
[0036] The RF transceiver 217 generates RF signals to stimulate a
target emitter (e.g., based on MAC address of emitter) and captures
response signals from the target emitter. The multi-element antenna
array 218b is capable of providing coverage of the spectrum of
interest in azimuth (horizontal field of view), and optionally in
elevation (vertical field of view) and polarization (frequency), if
so desired. The RF switching network 218a is configured to select
elements of the antenna array 218b (based on control signals
provided by computer 200) in synchronization with the transceiver
217. The joint operation of transceiver 217 and beamformer 218
effectively forms beams for long range transmission/detection.
[0037] Each of the transceiver 217 and beamformer 218 can be
implemented with commercial off-the-shelf (COTS) equipment, such as
a COTS 802.11 transceiver and a multi-element beamformer. For
example, in one specific embodiment, the multi-element beamforming
array 216 (including transceiver 217 and beamformer 218) is
implemented using a MediaFlex.TM. access point produced by Ruckus
Wireless, Inc. This commercially available beamformer has a
clam-shell configuration and can be coupled to the system 10 via an
Ethernet connection. In another example embodiment, the transceiver
217 and beamformer 218 may be implemented as described in U.S. Pat.
No. 7,362,280, which is incorporated herein in its entirety by
reference.
[0038] The computer 200 can be implemented with conventional
technology, including display area 201b (e.g., LCD display),
processor 203 (e.g., Intel.RTM. Pentium.RTM. class processors, or
other suitable microprocessors), and memory 205 (e.g., any RAM,
ROM, cache, or combination thereof typically present in computing
devices). However, as will be explained in turn, the LOB module
207, calibration files 209, and geolocation module 211 are
programmed or otherwise configured to carryout functionality
described herein. Likewise, user controls provisioned for the user
interface 201 (such as controls 201a) may be programmed or
otherwise configured to control and/or task the system 10 to
carryout functionality described herein. In some specific
embodiments, the computer 200 can be implemented, for example, with
a miniature or so-called ultra mobile computer, such as the OQO
model 2+ produced by OQO, Inc., or the VAIO.RTM. UX Series Micro PC
produced by Sony Corporation. Any number of small portable
computing platforms can be used to implement computer 200.
[0039] The LOB module 207 is programmed or otherwise configured to
convert a response signal from transceiver 217 into a line of
bearing (LOB) relative to the current position and orientation of
array 218b. The geolocation module 211 is programmed or otherwise
configured to identify the actual location of the target emitter on
the LOB, based on the intersection of LOBs from multiple vantage
points (e.g., on a map display) and/or GPS position and heading
tags associated with each computed LOB. For instance, in the
example embodiment shown in FIG. 2a, the system includes GPS module
213 and its corresponding antennas 213a-b, so that each LOB to a
target device can be associated with position and heading tags. The
GPS module 213 and antennas 213a-b can be implemented with
conventional GPS receiver and antenna technology. In one example
embodiment, GPS module 213 is implemented with a Crescent.RTM.
Vector OEM board produced by Hemisphere GPS, Inc. This particular
GPS board, which can be operatively coupled to computer 200 by an
RS-232 serial port or otherwise integrated into computer 200,
provides a GPS compass and positioning system that computes heading
and positioning using two antennas for greater precision. Other
suitable GPS receivers can be used as well, as will be apparent in
light of this disclosure. In any such cases, the geolocation module
211 accumulates bearings provided by GPS module 213 to produce a
geolocation, which can then be provided, for instance, on a map
display.
[0040] The user interface 201, including controls 201a and display
201b, allows the user to control and task the system 10. In one
specific case, the LOB results can be mapped or shown on a polar
plot to indicate in real time the direction to the target emitter.
The user interface 201 may include, for example, a probe button
that when pressed or otherwise selected initiates transmission of a
stimulus signal by the transceiver 217 and beamformer 218 to a
target device, so that the signal response from the device can be
received at the antenna array 218b over multiple antenna
configurations to provide a sample array of response data for that
device. The multiple antenna configurations can be selected, for
example, automatically by the control provided to the transceiver
217 and beamformer 218 by computer 200, or by operation of the
beamformer 218 itself. The array of response data can then be
analyzed by the LOB module 207 to identify an LOB to the target
device. In addition, the computer 200 may be configured to direct
transceiver 217 to transmit a specific stimulus signal having
parameters customized to a given target device. In any such cases,
the computer 200 receives the response signals from transceiver 217
for processing by the LOB module 207. The geolocation module 211
can then compute a specific location based on the computed
LOBs.
[0041] Each of the modules 207 and 211 can be implemented, for
example, as a set of instructions or code that when accessed from
memory 205 and executed by the processor 203, cause direction
finding and geolocation techniques described herein to be carried
out. In addition, the user interface 201 can be programmed or
otherwise configured to allow for functionality as described herein
(e.g., wherein controls 201a are implemented as graphical user
interface with touch screen functionality). The calibration files
209 effectively make up entries in a database that can be, for
example, any suitable data storage populated with gold-standard
response data having a known azimuth to which test data can be
correlated. The gold-standard response data may be, for instance,
empirical data measured by the system 10 in a multipath environment
under known conditions (e.g., where the azimuth/LOB from the
antenna array 215b to the target emitter device 50 is known, and a
full set of calibration measurements are taken at each known
azimuth). Alternatively, the gold-standard response data can be
theoretical data (assuming the theoretical data is sufficiently
accurate to provide accurate results). In any such cases, the
database 209 can be populated with gold standard data for any
number of azimuths. The number of azimuths represented in the
database 209 can vary depending on factors such as the desired
azimuthal resolution and FOV. In one example embodiment, the FOV is
assumed to be 360.degree. with a desired resolution of 1.degree.
(i.e., 360 azimuths). Other embodiments may have a narrower FOV
and/or a finer resolution (e.g., an FOV of 360.degree. and a
resolution of 0.1.degree., wherein there are 3600 azimuths; or an
FOV of 180.degree. and a resolution of 1.degree., wherein there are
180 azimuths; or an FOV of 360.degree. and a resolution of
20.degree., wherein there are 18 azimuths; or an FOV of 90.degree.
and a resolution of 2.0.degree., wherein there 45 azimuths. As will
be appreciated in light of this disclosure, the azimuthal
resolution and FOV will depend on the particular demands of the
application at hand. The azimuth entry in the database having the
calibrated array of data that best matches or otherwise correlates
to the measured array of data directly corresponds to the LOB to
the target device associated with the measured array of data.
[0042] In other embodiments, the calibration files 209, each of the
modules 207 and 211, and any graphical user interface (GUI) such as
controls 201a, can be implemented in hardware such as purpose-built
semiconductor or gate-level logic (e.g., FPGA or ASIC), or
otherwise hard-coded. In other embodiments, calibration files 209,
modules 207 and 211, and GUI 201a may be implemented with a
combination of hardware and software, such as with a
microcontroller having input/output capability for providing
control signals to transceiver 217 and beamformer 218, and for
receiving response data from transceiver 217, and a number of
embedded routines for carrying out direction finding and
geolocation techniques described herein.
[0043] As previously explained, the network detector 215 and its
omni-direction antenna 215a can be used to carryout a covert or
otherwise transparent survey process to identify various wireless
emitters in the FOV of system 10. In one such embodiment, the
network detector 215 is implemented with KISMET software executing
on processor 203 of computer 200. The omni-directional survey
antenna can be implemented, for example, with a Wi-Fi (802.11b/g)
PCMCIA card (e.g., whip antenna) that is operatively coupled to
computer 200, or otherwise integrated into computer 200 to provide
wireless connectivity. The detector 215 detects and interprets
information being transmitted by wireless emitters in the FOV, and
identifies information such as MAC address, SSID, channel, and
current encryption status to be identified. Any number of network
detectors can be employed for this surveying purpose.
[0044] The optional mapping module 221 can be used to provide map
displays upon which computed LOBs and/or geolocation markers can be
overlayed or otherwise integrated. In one such embodiment, the
mapping module 221 is a satellite based mapping system (e.g.,
Google Earth.TM. mapping service) executing on a secondary computer
system (e.g., laptop similar to computer 200). Alternatively, the
mapping module 221 can be implemented on computer 200. In one such
case, the display area 201b of the user interface 201 provides a
map display area having LOBs and the vehicle path overlayed thereon
(assuming a vehicle-based system 10). Other information may also be
included, as will be discussed with reference to FIG. 4.
[0045] The Ethernet hub 219 can be implemented with conventional
technology, and operatively couples various components of system 10
to effectively provide a communication network by which those
components can communicate. In the example embodiment shown, each
of computer 200, mapping module 221, and multi-element beamforming
array 216 are coupled to the Ethernet hub 219 by respective
Ethernet ports provided with each. Any number of conventional
networking/connectivity technologies can be used here to
operatively couple the components of system 10, and embodiments are
not intended to be limited to Ethernet based solutions.
[0046] FIG. 2b illustrates further details of the wireless emitter
locating system 10 shown in FIG. 2a, with respect to the geo module
211 and the LOB module 207, in accordance with an embodiment of the
present invention. As can be seen, the geo module 211 includes a
geo compute module 211a and a SQL database 211b, and the LOB module
207 includes a scan scheduler 207a and an LOB compute module 207b.
In general, computing multiple LOBs as the system 10 is actively
moving (such as the case of a vehicle-based system 10) gives rise
to various timing issues and can generate a significant amount of
data. For instance, example timing considerations may involve when
the next survey and/or target probe should take place and on what
channels, and example data includes emitter detections, multiple
LOBs, and corresponding navigation data for each of a plurality of
points along the travel path of system 10. To this end, the scan
scheduler 207a directs scheduling of system 10 operations in
response to user survey and probe commands (from user interface
201a), and SQL database 211b efficiently stores (and makes
accessible) pertinent data to the system 10.
[0047] In more detail, the scan scheduler 207a of this example
embodiment is programmed or otherwise configured to direct the
network detector 215 to survey the FOV of system 10 for wireless
emitters. The scheduler 207a specifies the channel to survey. For
instance, the scheduler may sequentially schedule scans for each
available channel associated with a given protocol (e.g., IEEE
802.11). The detector 215 provides any detections for each such
survey back to the scan scheduler 207a, which then stores those
detections (along with any pertinent learned information, such as
MAC address, channel, encryption status, etc) in database 211b.
Note that although SQL technology is used in this example, other
suitable database technologies can be used as well. The scan
scheduler 207a can then select any of the detected emitters (e.g.,
based on MAC address or other suitable identifier selected by user
via user interface 201a and indicated in the probe command), and
instruct the LOB compute module 207b to compute an LOB for that
particular emitter at that current location of the system 10. For
each LOB provided by module 207b to scheduler 207a, the scheduler
207a queries the database 211b for navigation data at that
particular time (time X). As can be further seen, the database 211b
responds by sending the scheduler 207a the appropriate navigation
data. The scheduler 207a then stores the LOB along with its
corresponding navigation data to the database 211b. In the example
embodiment shown, scan scheduler 207a also directs the beamforming
array 216 in conjunction with module 207b. In alternative
configurations, module 207b can direct beamforming array 216 after
scheduler 207a instructs module 207b. Additional details of how
module 207b operates and interacts with the cal files 209 and
beamforming array 216 are provided with reference to FIGS.
5a-c.
[0048] As previously explained, the GPS module 213 provides current
heading and position data, which is also stored in the database
211b and made available the LOB module 207. The geo compute module
211a is programmed or otherwise configured to compute, in response
to a geolocate command from the user (via interface 201a), a
geolocation for the specified target emitter. As previously
explained, the geolocation can be computed based on the
intersection of the corresponding LOBs and/or the navigation data
(position/heading tags) associated with those LOBs. The computed
geolocation can then be stored in the database 211b by module
211a.
[0049] FIG. 2c illustrates example states and modes of the wireless
emitter locating system 10 shown in FIG. 2a, in accordance with an
embodiment of the present invention. As can be seen, the diagram
includes two main portions: one for the computer 200 (which is a
laptop in this example) and another for other hardware (detector
215 and array 216) of system 10. At power-up, the system 10
transitions from its OFF state to its Online state, where upon the
database 211b becomes available and modules 201a and 213 come
online. During an Offline/Editing state, only the computer 200
(with its modules and database 211b) may be powered-on (e.g., leave
module 213 powered-down or in low power mode to conserve power),
which allows for offline tasks such as importing/exporting data and
computing of geolocations.
[0050] Once computer 200 is in its Online state, the user may task
system 10 hardware to survey, probe, etc. To conserve power, note
that detector 215 and array 216 can be powered-down or held in a
low power mode during extended periods of not receiving any user
tasks. Once a task is received, the system 10 can transition from a
Standby state to either a Survey state or a Probe state, depending
on the user task received. For instance, if the survey button (or
other user interface mechanism) is selected, the system transitions
to the Survey state where available channels are surveyed for
wireless emitters. The channels to survey can be automatically
selected (e.g., by operation of scheduler 207a as previously
described), or specified by the user. In one such case, after the
survey is complete, the user can select a new set of channels for
survey, or set the channels list to 0 (i.e., no further surveying).
As can be further seen, selecting the probe button (or other user
interface mechanism) causes system 10 to transition to the Probe
state for targeted probing of an emitter having a specified MAC
address. If after N seconds (e.g., 5 to 15 seconds) no response is
received from the targeted emitter, system 10 may transition back
to the Survey state in effort to identify other emitters in the FOV
or to correct identifying information associated with the target
emitter. Alternatively, the system 10 can transition back to the
Standby state. Any number of timing/abort schemes for controlling
state transition can be used here.
[0051] FIGS. 3a and 3b illustrate a vehicle-based version of the
wireless emitter locating system 10 shown in FIG. 2a, configured in
accordance with an embodiment of the present invention. As can be
seen, the system 10 includes inside vehicle componentry 10a (as
best shown in FIG. 2a), a multi-element beamforming array 216, GPS
antennas 213a-b, and survey antenna 215a as previously discussed
with reference to FIG. 2a, and that previous discussion is equally
applicable here. In addition to these components, this embodiment
further includes a mobile platform 311 and cabling 307. The vehicle
310 can be any type of suitable vehicle given the particular
application at hand, and numerous deployment schemes for system 10
will be apparent in light of this disclosure.
[0052] In this example embodiment, the platform 311 is used to
support a clam-shell configuration that houses the multi-element
beamforming array 216. The cabling 307 is for operatively coupling
the outer vehicle componentry to the inside vehicle componentry
10a, and may include a bound cable harness or a number of
independent dedicated cables operatively coupled between respective
components. The clam-shell assembly including the beamforming array
216 can be implemented, for example, using a MediaFlex.TM. access
point produced by Ruckus Wireless, Inc. As previously explained,
the user interface 201 can be used to task or otherwise activate
system functions. Any number of user interface and activation
mechanisms may be implemented to allow for control and/or tasking
of the system 10, as will be apparent in light of this
disclosure.
[0053] FIG. 4 illustrates an example user interface 201 of the
wireless emitter locating system 10 shown in FIG. 2a, in accordance
with an embodiment of the present invention. As can be seen, the
interface 201 is implemented within a browser and includes a map
display area for displaying multiple LOBs computed by the system 10
as well as the vehicle's path. Map setting and information can also
be provided, to allow the user to configure the map as desired
(e.g., to show more or few details, zoom level, labels, etc).
[0054] An LOB resulting from the process carried out by LOB module
207 is visually depicted on a polar plot, along with the vehicle
heading, to indicate in real-time the direction to the target
device relative to the current position and orientation of array
216. As can be further seen, specific LOB details may also be
displayed to ease the user's viewing, if so desired.
[0055] Also shown above the LOB polar plot are response signals and
the corresponding correlation factors computed by the system 10 as
described herein. As can be seen, each response signal parameter of
amplitude (Am . . . ) that has been measured has an ID value and
corresponds to a computed correlation factor (Corr.) and a
corresponding azimuthal (Az . . . ) value. The user may search this
data and/or scroll the data for review. In this specific example,
the user can also specify a maximum LOB age (to prevent stale
readings), if so desired.
[0056] The interface 201 of this example further includes a section
for survey results showing discovered wireless emitters and
corresponding information associated with each such emitter. The
information includes, for instance, a callsign, SSID, type of
emitter (e.g., 802.11b, 802.11g, etc), MAC address, communication
channel, category (e.g., 0=unencrypted; 1=encrypted), the number of
LOBs computed for that emitter (if any), emitter ID (if assigned),
and the client MAC (which may be helpful in embodiments where there
is more than one system 10 providing information, such as described
in the previously incorporated U.S. application Ser. No. ______
(Attorney Docket BAEP-1125).
[0057] The interface 201 of this example further includes a Probe
button (e.g., touch screen activated or otherwise selectable by the
user) for initiating a probing task of a selected emitter device.
The interface 201 may also include a Survey button to initiate
surveys. Other embodiments may combine the tasking functions for
Probing and Survey into a single button. The interface further
includes a Geolocate button, which initiates a geolocation
computation for a selected emitter based on its LOBs and associated
navigation data.
[0058] Line of Bearing Determination
[0059] FIG. 5a illustrates a method for determining an LOB to a
wireless emitter and geolocating that emitter based on multiple
LOBs, in accordance with an embodiment of the present invention. As
previously explained, the method can be carried out, for example,
by system 10.
[0060] The method begins with surveying 501 the area of interest to
identify wireless emitters within that area (e.g., by MAC address,
and/or other suitable identifiers). The user can task this survey,
for example, using the user interface 201 (e.g., survey button on
graphical user interface that is coded to generate control signals
commanding the transceiver 217 and beamformer 218 to transmit the
survey signal). Note that this step may be done contemporaneously
with remaining portions of the method, or at any time prior to the
remaining portions.
[0061] The method continues with selecting 503 a target emitter
discovered during the survey (e.g., based on the target device's
MAC address or other suitable identifier, and using the channel
associated with that emitter) for probing to direction find and
geolocate that emitter. The user can task this probing of the
target device, for example, using the user interface 201 (e.g.,
user can select the target emitter using graphical user interface
that is coded to display a list of emitters identified during the
survey, and then user can select probe button on graphical user
interface that is coded to generate control signals commanding the
transceiver 217 and beamformer 218 to transmit the probe
signal).
[0062] The method continues with transmitting 505 a stimulus signal
to the target emitter. Recall that computer 200 of system 10 may be
configured to direct transceiver 217 to transmit a specific
stimulus signal having parameters customized to a given target
device, if so desired (e.g., as commanded by LOB module 207).
Alternatively, the stimulus signal can be any signal that causes
the target emitter to provide a response signal that can be
detected and processed by system 10 as described herein. In some
cases, no stimulus signal is required if, for example, a given
target device automatically broadcasts or otherwise transmits its
information (such voluntary signals can be considered a `response`
as well, for purposes of this disclosure). In such cases, the
system executing the method can passively listen for target emitter
transmissions.
[0063] The method continues with measuring 507 the response signal
parameter (or parameters) for each of Y antenna patterns, thereby
providing a Y sample array of response data. As previously
explained, the antenna array 218b is configured with a number of
elements that can be selected by switching network 218a to provide
various antenna configurations. In one example case, the antenna
has six horizontally-polarized elements, thereby providing 2.sup.6
different configurations (i.e., Y=64). In another example case, the
antenna has six horizontally-polarized and vertically-polarized
elements, thereby providing 2.sup.12 different configurations
(i.e., Y=4096).
[0064] The method continues with correlating 509 the sample array
to a plurality of entries in a database of calibrated arrays having
known azimuths, to generate a correlation plot. This process can be
carried out, for example, by the LOB module 207, or a dedicated
correlation module. As is generally known, a correlation process
measures how well two populations match one another. Any
conventional correlation technique can be used to perform this
correlation, where such techniques typically provide a correlation
factor between 0 (low correlation) and 1 (high correlation). FIG.
5b illustrates a correlation process to identify which calibrated
array best matches a sample array, in accordance with an embodiment
of the present invention. As can be seen, the cal files 209 include
360 calibrated arrays, one for each LOB ranging from 1.degree. to
360.degree. (with a 1.degree. resolution). In this example of FIG.
5b, the antenna array has two elements capable of providing four
distinct antenna patterns (indicated as 0,0; 0,1; 1,0; and 1,1).
Thus, once the sample array of response data is provided by the
transceiver 217 to the computer 200, that sample array can be
compared against the cal files 209 to generate a correlation factor
for each comparison. Each of these correlation factors can then be
plotted to provide a correlation scan or plot as shown in FIG. 5c.
The peak of the correlation plot corresponds to an azimuth (or LOB)
to the target emitter. Note that LOB is effectively interchangeable
with azimuth in this context.
[0065] The method therefore continues with identifying 511 the
target azimuth of the sample array based on the peak of the
correlation plot, and determining a line of bearing (LOB) to target
based on the target azimuth. In the example of FIGS. 5b and 5c, the
sample array best matches the cal file 209 corresponding to the LOB
of 280.degree.. As will be appreciated, the number of azimuths and
antenna patterns used for this example was selected for ease of
depiction. Other embodiments may have any number of azimuths
(represented in cal file 209) and/or antenna patterns. In any such
case, the target LOB can be graphically displayed to the user
(e.g., as shown in FIG. 4).
[0066] The method continues with geolocating 515 the target emitter
based on two or more LOBs, from multiple vantage points. In one
such embodiment, this geolocation is carried out by the user moving
to a second location and then repeating steps 505 through 513 to
get a second LOB to target. The user may repeat at any number of
additional locations, providing an LOB at each location. The user
may collect such LOBs at multiple points, for instance, along an
L-shaped path, or other path that will allow for geolocation based
on LOBs to be carried out. The computed LOBs can be stored, for
example, in a memory of computer 200, and/or displayed to the user
as shown in FIG. 4 (along with travel path). Alternatively, the
user can manually plot the LOBs. In any such cases, the LOBs will
generally intersect. The more LOBs provided to the target, the more
robust and accurate the intersection will be. The user can then
translate this intersection to a geographic location, using
conventional geolocation techniques. As previously explained, each
LOB may be further associated with position and heading data (from
navigation system), which can also be used to readily and
accurately geolocate the target emitter.
[0067] The foregoing description of the embodiments of the
invention has been presented for the purposes of illustration and
description. It is not intended to be exhaustive or to limit the
invention to the precise form disclosed. Many modifications and
variations are possible in light of this disclosure. For instance,
some embodiments are discussed in the context of a ground
vehicle-based device. Other example embodiments may be any
vehicle-based (e.g., airplane, ship, etc). Still other example
embodiments may be backpack-based, such that a user can don the
backpack and control and task system using a wired or wireless
remote having a small display screen to allow user to see computed
LOBs/geolocation results. Alternatively, such a backpack-based
system can be configured to respond to voice commands, and aurally
present computed LOBs/geolocation results so that user's hands
remain free. It is intended that the scope of the invention be
limited not by this detailed description, but rather by the claims
appended hereto.
* * * * *